Hi guys, my friend recently gave me his HD600s and my search for a dac/amp has resumed. I was looking at a couple of options from my local store, some of them are: Calyx Pat ($88), Astell & Kern AK10 ($99) and FiiO E17K. I'd like to use this at home and on the go. How do these compare for this kind of usage? Also support for lower ohm would be cool to have too.